Rotary piston apparatus



March 4, 1969 E. GROEGER ROTARY PISTON APPARATUS Sheet Filed Sept. 29, 1966 Eugen GRGER MJul/ i r his ATTORNEY March 4, 1969 E. GROEGER ROTARY PI STON APPARATUS Sheet 3 0:2

Filed Sept. 29, 1966 his ATTORNEY United States Patent Claims ABSTRACT OF THE DISCLOSURE An assembly including at least two rotary piston apparatus each comprising a housing and two coaxial pistons subdividing the housing in a plurality of chambers, and a gear train connecting said pistons with a rotary spindle which can receive driving torque from or transmit driving torque to the rotary piston apparatus. The gear train being arranged to move the pistons of each rotary piston apparatus through a plurality of neutral positions in which the angular speed of both pistons in the respective apparatus is the same and to maintain One pair of pistons in such neutral position when the other pair of piston is out of neutral position and vice versa.

The present invention relates to rotary piston apparatus, and more particularly to an assembly which utilizes rotary piston apparatus of the type wherein two relatively movable coaxial pistons subdivide the interior of a housing into a plurality of chambers whose volume varies periodically in response to rotation of pistons about their common axis. Such apparatus can function as internal combustion engines, fluid-operated motors, pumps and/or compressors.

It is already known to provide a rotary piston apparatus with two relatively movable pistons and to couple such pistons by means of a gear train which insures that rotation of pistons about a common axis brings about angular movement of pistons toward and away from each other so that the volume of aforementioned chambers varies in response to rotation of pistons in their housing. A serious drawback of such rotary piston apparatus is that the wear upon the gears of their transmissions is very high and that the rotary member which receives driving torque from or transmits driving torque to the pistons undergoes stresses whose magnitude varies not only in a positive but also in a negative range of angular momentum.

Accordingly, it is an important object of the present invention to provide a novel and improved assembly which embodies rotary piston apparatus of the above outlined characteristics but is constructed and assembled in such a way that the wear on the gears of its transmission is reduced and that the stresses upon the rotary member which transmits or receives driving torque from the pistons of such rotary apparatus fluctuate within a much narrower range.

Another object of the invention is to provide an assembly wherein a plurality of rotary piston apparatus can be assembled in a small area and wherein at least one such apparatus can be started in each angular position of the aforementioned rotary member.

A further object of the invention is to provide an assembly which can be utilized as a multi-stage compressor.

An additional object of the invention is to provide an assembly which will operate satisfactorily within a very wide range of rotational speeds of the rotary member which transmits or receives torque from the pistons of the rotary piston apparatus.

A concomitant object of the invention is to provide 3,430,573 Patented Mar. 4, 1969 "ice an assembly whose rotary piston apparatus will operate satisfactorily without necessitating the provision of flywheels on the rotary member which receives or transmits torque to the pistons.

Still another object of the instant invention is to provide a novel assembly of rotary piston apparatus wherein each apparatus influences the operation of the other apparatus in a novel and beneficial way.

Briefly stated, one feature of my invention resides in the provision of an assembly which comprises two or more rotary piston apparatus. Basically, the improved assembly comprises a rotary spindle which can receive driving torque from or transmits torque to the rotary piston apparatus, at least two rotary piston apparatus each of which includes a housing and two coaxial pistons mounted in and subdividing the interior of the housing into a plurality of chambers, and transmission means connecting the spindle with the pistons to rotate the pistons with and with reference to each other when the spindle rotates so that the volume of each chamber increases and decreases periodically in response to rotation of the respective pairs of pistons about their common axes. The transmission means comprises a gear train for moving the pistons of each rotary piston apparatus through a plurality of neutral positions in which the angular speed of both pistons in the respective apparatus is the same and to maintain one pair of pistons in such neutral position when the other pair of pistons is out of neutral position, or vice versa.

The gear train may consist exclusively of oval gears or it may comprise oval gears provided on the shafts of the pistons and eccentric spur gears provided on the spindle and each meshing with the oval gear on one iston of each apparatus.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved assembly of rotary piston apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawings, in which:

FIG. 1 is a transverse section through a rotary piston apparatus which constitutes a four stroke cycle internal combustion engine and may be utilized in the assembly of my invention;

FIG. 2 is a similar transverse section through a second rotary piston apparatus which can constitute a pump or motor and may be utilized in the improved assembly;

FIG. 3 is a central sectional view of an assembly which embodies one form of my invention and comprises two rotary piston apparatus of the type shown in FIG. 2, the section of FIG. 3 being taken in the direction of arrows subtsantially as seen from the line III-III of FIG. 4;

FIG. 4 is a diagrammatic front elevational view of the pitch circles of gears which form part of transmission means in the assembly shown in FIG. 3, the view being taken in the direction of arrows from the line lV-IV of FIG. 3;

FIG. 5 is a similar diagrammatic front elevational view of the gear train in an assembly which embodies three rotary piston apparatus of the type shown in FIG. 2;

FIG. 6 is a diagrammatic front elevational view of a gear train in an assembly which comprises a plurality of rotary piston apparatus of the type shown in FIG. I, the view being taken in the direction of arrows from the line VIVI of FIG. 7; and

FIG. 7 is a section through the assembly substantially as seen in the direction of arrows from the line VIIVII of FIG. 6.

FIG. 1 shows a rotary piston apparatus which is used as a four stroke cycle internal combustion engine. It comprises a cylindrical housing 1 defining an internal compartment 1A which accommodates two pistons 2 and 3 each having two lobes disposed diametrically opposite each other. Each lobe of the piston 2 is located between the lobes of the piston 3, and vice versa. The four lobes define between themselves four chambers a, b, c and d. As shown in FIG. 1, the hub of the piston 2 is fixed to a shaft 4 which extends from the housing 1 and is fixed to an oval gear 6. The hub of the piston 3 is connected with a hollow shaft 5 which surrounds the shaft 4 and extends from the housing 1. A second oval gear 7 is connected with the hollow shaft 5 outside of the housing 1, and the oval gears 6, 7 respectively mesh with spur gears 8, 9 eccentrically mounted on a rotary member 10 (hereinafter called spindle to avoid confusion with the shafts 4 and 5). The spur gears 8, 9 are offset through 180 degrees with reference to each other and their function is to insure that the oval gears 6, 7 rotate about the common axis of the shafts 4, 5 and that these oval gears rotate with reference to each other to bring about periodic changes in the volume of chambers a to d in a manner well known from the art of internal combustion engines and disclosed, for example, in German Patent No. 669,498. The housing 1 is formed with three openings one of which accommodates a spark plug 13 or another suitable igniter. The other opening 11 is an inlet opening and is connected with a source which delivers a mixture of fuel and oxygen. The third opening 12 is an exhaust opening and serves to discharge combustion products. The openings 11, 12 are mirror symmetrical with reference to a plane which includes the axes of spindle 10, shafts 4, 5 and opening for the spark plug 13.

The volumes of the chambers a and shown in FIG. 1 are reduced to a minimum. The chamber c contains a highly compressed mixture of fuel and oxygen which is ignited by the spark plug 13 whereby the products of combustion tend to expand and exert a pressure against the adjoining lobe of the piston 3 to turn this piston in a counterclockwise direction. The ratio of the transmission including the gears 6, 7, 8 and 9 is such that the angular speed of the piston 3 increases while the angular speed of the piston 2 decreases so that the volume of the chamber 0 increases and the combustion products are discharged through the opening 12. At the same time, the volume of the chamber a begins to increase so that this chamber sucks a fresh mixture of fuel and oxygen through the opening 11. The chamber a is already filled with such mixture and its volume decreases in response to counterclockwise rotation of the pistons 2 and 3 so that the mixture is compressed and is ultimately ignited by the spark plug 13 when the volume of the chamber d equals the volume of the chamber a, reference being had to FIG. 1. The chamber b is filled with combustion products which are about to be expelled via opening 12 because the volume of this chamber decreases when the pistons 2, 3 turn in a counter-clockwise direction and beyond the positions shown in FIG. 1. It will be seen that the engine of FIG. 1 will complete four full cycles of suction, compression, ignition and exhaust in response to a full revolution of the pistons 2 and 3. The length of the pitch circle of the spur gear 8 or 9 equals half the length of the pitch circle of the oval gear 6 or 7, i.e., the spindle 10 will complete two revolutions in response to a single revolution of the shaft 4 or 5. After each angular displacement of the spindle 10 through 180 degrees, the effective radii of the spur gears 8, 9 are identical and the effective radii of the oval gears are also identical. The term effective radius is intended to denote the distance between the common axis of the shafts 4, or the axis of the spindle and the point where the gears 6, 8 or 7, 9 mesh.

FIG. 1 shows the gears 69 in such angular positions which correspond to a neutral position of the transmission whereby the momentary angular speed of the piston 2 equals the momentary angular speed of the piston 3. The same conditions will prevail when the spindle 10 is turned through 180 degrees. In each other but such neutral position, the transmission ratio of gears 6, 8 is different from the ratio of gears 7 and 9. This is due to eccentric mounting of spur gears 8, 9 with reference to the spindle 10 and with reference to each other. The angular speed of each oval gear varies periodically whereby the piston 2 is accelerated when the piston 3 is decelerated and vice versa. This brings about the aforementioned periodic changes in volume of the chambers a to d. The volume of each chamber changes twice between a maximum and minimum value in response to each full revolution of the pistons 2 and 3; therefore, the apparatus of FIG. 1 is ideally suited to function as a four stroke cycle internal combustion engine.

In the position shown in FIG. 1, the line halving the angle between the longer axes of the oval gears 6, 7 is normal to the line connecting the axes of the spur gears 8 and 9. Therefore, the volume of each of the chambers a, c is reduced to a minimum and the volume of each of the chambers b, d is increased to a maximum value. In response to rotation of the spindle 10 through one-half of a revolution (i.e., on rotation of pistons 2 and 3 through degrees), the spur gears 8, 9 will exchange positions whereby the volume of the chambers b, d is reduced to a minimum and these chambers respectively switch positions with the chamber 0 and a because the shafts 4, 5 rotate in a counterclockwise direction.

FIG. 2 shows a modified rotary piston apparatus which can be used as a pump or motor. Its housing 1' is provided with two inlet openings 11, 11' and two outlet openings 12, 12'. The spur gears 8, 9 of FIG. 1 are replaced by oval gears 14, 15. If the spindle 10 is driven by a prime mover (i.e., if the apparatus of FIG. 2 is used as a pump), the chamber a will expand during travel past the opening 11 to draw fresh fluid and expels such fluid during travel past the opening 12. At the same time, the chamber 0 draws fluid through the opening 11 and thereupon expels the fluid via opening 12. The chambers 12 and d are filled with fluid and are about to evacuate their contents via openings 12 and 12'.

The oval gears 14, 15 are angularly offset through 90 degrees with reference to each other and the length of their pitch circles is the same as that of the gears 6 and 7. Therefore, each full revolution of the spindle 10 will cause a full revolution of the shafts 4 and 5. The volume of the chambers a, c shown in FIG. 2 has been reduced to a minimum and the volume of the chambers b, d has increased to a maximum. The transmission including the gear trains 6, 7, 14, 1 5 is in a neutral position because the effective radii of gears 6, 7 and 14, 15 are respectively identical. Thus, at the exact moment when the transmission assumes such neutral position, the angular speed of the pistons 2 and 3 is the same. The transmission will assume such neutral position in response to each revolution of the spindle through 90 degrees because the longer axes of the oval gears 14, 15 make with each other an angle of 90 degrees.

In the apparatus of FIG. 2, each of the chambers a to d will perform only two different functions in response to each revolution of the shafts 4 and 5. This is due to the fact that the housing 1' has two inlet openings 11, 11' and two outlet openings 12, 12'. If the openings 11, 11 receive pressurized fluid from a pump, the pistons 2 and 3 will rotate the spindle 10 so that the apparatus of FIG. 2 will function as a motor. This apparatus can be operated with steam, compressed air or oil and can be used as a motor, compressor or pump.

It is to be noted that the apparatus of FIG. 2 by itself forms no part of my invention. Such apparatus are disclosed in Swiss Patent No. 175,763.

My present invention is concerned with improvements in assemblies which utilize several rotary piston apparatus and transmissions of the type shown in FIG. 1 or 2. It was found that the gears of transmissions in the apparatus of FIG. 1 or 2 are subjected to excessive stresses and extensive wear, mainly because the shaft 4 is decelerated when the shaft 5 is accelerated, or vice versa. The inertia of parts carried by and coupled with these shafts subjects the teeth of gears '6-9 or 6, 7, 14, 15 to extensive stresses. Furthermore, the angular momentum of the spindle varies continuously and its curve exhibits pronounced peaks in the positive as well as in the negative range. In the apparatus of FIG. 1, each revolution of the shafts 4 and 5 brings about eight changes in the direction of torsional stresses upon the spindle 10. The situa tion is analogous in the apparatus of FIG. 2.

In accordance with my invention, the wear upon the gear trains of transmissions which connect the spindle 10 with the shafts of the rotary pistons is reduced by coupling the shafts 4, 5 of two or more rotary piston apparatus with a common spindle 10 in a manner as shown in FIGS. 3 to 7. Such construction also reduces sudden changes in torsional stresses upon the spindle 10.

Referring first to FIGS. 3 and 4, the assembly therein shown comprises two rotary piston apparatus of the type shown in FIG. 2. The oval gears 14, of the spindle 10 mesh with the oval gears 6, 7 and 6a, 7a of both rotary piston apparatus. The transmission of this assembly comprises a casing 16 which accommodates the gears '6, 7, 6a, 7a and 14, 15. The spindle 10 is journalled in the front and rear end walls of the casing 16 and the lines connecting the axis of this spindle with the axes of the shafts 4, 5 and 4a, 5a make an angle (p which exceeds 90 degrees but, is less than 180 degrees, preferably about 135 degrees. The reference numerals utilized in FIG. 3 to denote the parts of the left-hand rotary piston apparatus are identical with those used to denote the corresponding parts of the right-hand apparatus but each thereof if followed by the character a. Each of the shafts 4, 4a is journalled in the casing 16 and in the respective housing 1', 1a. Each of the hollow shafts 5, 5a is journalled in two bearings provided in an axial extension of the respective housing. The assembly of FIG. 3 forms a compact and lightweight unit.

FIG. 4 shows that the angle between the longer axes of the oval gears 6, 7 is different from the angle between the longer axes of the oval gears 6a, 7a. This is an important feature of the present invention because, when the angle (,0 is 135 degrees, torsional stresses upon the spindle 10 will vary in accordance with a highly satisfactory pattern. The angular momentum upon the spindle 10 is free of undesirable changes in load and fluctuates only in the positive range. In comparison with the apparatus of FIG. 2, the peaks of angular momentum are reduced in half, it being assumed that the dimensions of oval gears and the rpm. are the same. This isattributed to the fact that angular momentums in the positive range of one apparatus are balanced by angular momentums in the negative range of the other apparatus. Such highly satisfactory angular momentum of the spindle will be achieved when the r.p.m. does not exceed a predetermined maxi-mum value. If the rpm. exceeds such value, the aforementioned peaks in the angular momentum cur-ve reappear; however, this value of r.p.m. is so high that it is of no consequence when the assembly of FIG. 3 is put to actual use and the spindle 10 rotates within an optimum speed range below the aforementioned maximum value.

FIG. 4 shows that the transmission between the spindle 10 and the pistons 2, 3 of the right-hand apparatus is in a neutral position, i.e., the effective radii of the gears 14, 15 and 6, 7 are respectively identical. Thus, the pistons 2, 3 transmit to the spindle 10 identical torque but in opposite directions. Were the assembly of FIG. 3 provided only with a single rotary piston apparatus of the type shown in FIG. 2, such apparatus could not be started in automatic response to admission of fluid to the openings 11, 11' when the gears 6, 7, 14, 15 assume a neutral position. This drawback is avoided by the provision of the second rotary piston apparatus and by appropriate selection of the angle (,0 180). Such selection of the angle (p insures that the transmission between the pistons 2a, 3a and spindle 10 cannot assume a neutral position simultaneously with the transmission between the spindle 10 and pistons 2, 3.

The assembly of my invention can be utilized as a multistage compressor.

FIG. 5 illustrates the transmission system of an assembly which comprises a set of three equidistant rotary piston apparatus of the type shown in FIG. 2. The angle (,0 is degrees and the transmission including the oval gears 6, 7, 14, 15 is in neutral position when at least one of the other two transmissions (6a, 7a, 14, 15 or 6b, 7b, 14, 15) is in a position other than neutral position. This enables the assembly to automatically start its rotary piston apparatus in each and every angular posi tion of the spindle 10. It is to be noted that the three apparatus of FIG. 5 need not be equidistant from each other, i.e., one of the angles (,0 can be diiferent 'from the other two angles or each of these angles can be different, as long as the magnitude of each angle exceeds 90 degrees but is less than 180 degrees.

The assembly of FIG. 5 insures that the torque upon the spindle 10 assumes a practically constant value and that there is no change in the orientation of load upon the spindle. The aforementioned maximum permissible rotational speed for the spindle 10 of FIG. 5 is much higher than the maximum permissible speed for the spindle 10 of FIG. 3. The space requirements of the assembly with three rotary piston apparatus exceed only slightly the space requirements of the assembly with two apparatus but the output of the assembly with three apparatus is much higher. This assembly will operate properly without a flywheel on the spindle 10 and is particularly useful for operation at high speeds.

FIG. 5 shows that the angle between the longer axes of the oval gears 6, 7 is different from the angles between the longer axes of the oval gears 6a, 7a and 6b, 7b. Therefore, the assembly of FIG. 5 can be started in each angular position of the spindle 10 and will immediately furnish a very high torque.

FIGS. 6 and 7 illustrate an assembly which comprises two or more rotary piston apparatus of the type shown in FIG. 1. In its simplest form, this assembly will comprise two rotary piston apparatus, for example, the two upper apparatus whose oval gears 6, 7 and 6a, 7a are shown in the upper part of FIG. 6. The angle o is 90 degrees which brings about the same advantages as those described in connection with the assembly of FIG. 3 wherein the angle (,0 is degrees. The transmission which couples the spindle 10 with the shafts of the pistons of the upper right-hand apparatus (oval gears 6, 7 and eccentric spur gears 8, 9) is shown in neutral position but the transmission between the spindle and the upper left-hand apparatus (gears 6a, 7a, =8, 9) is in other than neutral position. The angle (,0 in the assembly of FIGS 6 and 7 must exceed zero but must be less than degrees; otherwise, its apparatus could not be started in each angular position of the spindle 10.

FIG. 7 shows that the oval gears 6, 6a'and 7, 7a are disposed in parallel planes and that the axial length of spur gears 8, 9 is such that each thereof can mesh with two oval gears. Such arrangement is desirable to avoid interference between the various groups of gears. An assembly utilizing two rotary piston apparatus of the type shown in FIG. 1 or 2 preferably comprises a flywheel on the spindle 10 to further reduce fluctuations in torque upon the spindle.

Since the angle to for assemblies with rotary piston apparatus of the type shown in FIG. 2 should exceed 90 degrees, an assembly which embodies more than three rotary piston apparatus will comprise apparatus of the type shown in FIG. 1. Therefore, the transmission system of the assembly shown in FIGS. 6 and 7 comprises two eccentric spur gears so that each angle between the lines connecting the shaft of the spindle with the common axes of pistons in two adjoining apparatus will be 90 degrees. Such distribution of the four rotary piston apparatus brings about substantial savings in space and insures highly satisfactory patterns of torsional stresses upon the spindle 10. The transmissions connecting the spindle 10 with the shafts of pistons in the apparatus which are located diametrically opposite each other will simultaneously move to and from neutral position. Thus, FIG. 6 shows that the transmission including the gears 6, 7, 8, 9 and 6b, 7b, 8, 9 are in neutral position. However, the other two transmissions 6a, 7a, 8, 9 and 6c, 70, 8, 9 are out of neutral position so that the assembly of FIG. 6 can be readily started in each angular position of the spindle 10. In the assembly of FIG. 6, the magnitude of peaks of angular momentum of the spindle 10 exceeds twice the magnitude of such peaks in an assembly with two rotary piston apparatus of the type shown in FIG. 1. Therefore, the assembly of FIG. 4 preferably comprises a flywheel which is mounted on the spindle 10. The mounting of oval gears in parallel planes as shown in FIG. 7 is satisfactory for assemblies with two or four rotary piston apparatus. The gears 6 and 6b, 6a and 6c, 7 and 7b, 7a and 7c are respectively located in common planes.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is:

1. An assembly of the character described, comprising a rotary spindle; at least two rotary piston apparatus having parallel axes and each including a stationary housing and two coaxial pistons provided in a the interior of the respective housing and each having a pair of diametrically opposite lobes so as to subdivide the interior of the respective housing into four chambers; and transmission means connecting said spindle with said pistons to rotate the pistons of each apparatus and with reference to each other when the spindle rotates so that the volume of said chambers increases and decreases periodically in response to rotation of the respective pair of pistons about the common axes, said transmission means comprising a gear train for moving the pistons of each apparatus through a plurality of neutral positions in which the angle of speed of both pistons in the respective apparatus is the same and to maintain one pair of said pistons in such neutral position when the other pair of pistons is out of neutral position, or vice versa.

2. An assembly as defined in claim 1, wherein the common axes of said pairs of pistons are mirror symmetrical with reference to a plane including the axis of said spindle.

3. An assembly as defined in claim 1, wherein said gear train consists exclusively of oval gears mounted each for rotation about an axis passing through the intersection of the long and the short axis of the respective oval gear, and wherein the angle between the lines connecting said common axes with the axis of said spindle exceeds degrees but is less than 180 degrees.

4. An assembly as defined in claim 3, wherein all of said oval gears are identical and wherein said angle is degrees.

5. An assembly as defined in claim 1, wherein said gear train comprises oval gears coaxially secured to said pistons and spur gears excentrically mounted on the spindle and each meshing with the oval gear for one piston of each rotary piston apparatus, the axes of said spur gears bearing mirror symmetrical with reference to the axis of said spindle, the lines connecting said common axes with the axis of said spindle making an angle which exceeds zero but is less than degrees.

6. An assembly as defined in claim 5, wherein said angle is 90 degrees.

7. An assembly as defined in claim 1, wherein the gears of said gear train are disposed in a plurality of parallel planes.

8. An assembly as defined in claim 1, wherein the axis of said spindle is parallel to said common axes and wherein four chambers a first and a second pair of chambers respectively having identical volumes in each angular position of the corresponding pair of pistons.

9. An assembly as defined in claim 1, wherein the number of said rotary piston apparatus exceeds two and wherein the common axes of said pairs of pistons are equidistant from each other and parallel to and equidistant from the axis of said spindle.

10. An assembly as defined in claim 1, wherein said pistons are arranged to transmit torque to said spindle through said gear train and wherein said gear train comprises an oval gear for each of said pistons, said oval gears being coaxially afiixed to said pistons and the angle between the longer axes of oval gears for one pair of pistons being different from the angle between the longer axes of the oval gears for the other pair of pistons in each angular position of said spindle.

References Cited UNITED STATES PATENTS 1,231,995 7/1917 Boudreau. 1,701,648 2/ 1929 Wildey. 2,305,797 12/ 1942 Shimizu 9 l--60 2,531,903 11/1950 Berck 9160 3,112,062 11/1963 Way 230-144 3,193,191 7/ 1965 McClure 230-144 DONLEY J. STOCKING, Primary Examiner.

W. J. GOODLIN, Assistant Examiner. 

